1. Field of the Invention
The present invention generally relates to a pulse wave detecting apparatus. More specifically, the present invention is directed to a pulse wave detecting apparatus capable of clearly discriminating pulsations from noise, while having a small storage amount and also a small computation amount.
2. Description of the Related Art
In medical fields and also when performing health care administrations, detections of pulse waves by measuring blood f lows within arteries are widely carried out. To detect such pulse waves, palpation is carried out. In addition, using pulse wave detecting apparatus, the pulse rate is automatically and electronically detected to detect such pulse waves.
As an apparatus capable of electronically detecting pulse waves to obtain pulse rates, there are various types of apparatuses, for instance, one pulse wave detecting apparatus operated in such a manner that while a piezoelectric-effect type element is positioned as a sensor over an artery, a pulse rate is detected based upon a change contained in pressure of a skin surf ace (namely, displacement of skin surface caused by pressure) in connection with a pressure change occurred within this artery, and another detecting apparatus capable of detecting a pulsatory number is operated by using ultrasonic waves.
Then, in such pulse wave detecting apparatus, pulse wave signals need to be discriminated from noise.
As the conventional technique for discriminating the pulse wave signals from the noise, there is known for instance, Japanese Laid-open Patent Application Laid-open No. Hei-7-227383 describes the method of using the frequency analysis. In this conventional discrimination method, while the data containing the noise are stored for a predetermined time period, the frequency analysis such as FFT (Fast Fourier Transform) is carried out with respect to the stored data so as to calculate the average pulse within a preselected time period.
However, in such a conventional pulse wave detecting apparatus capable of discriminating the pulse wave signals from the noise by utilizing the frequency analysis, vary large amounts of data are required to be stored in order to execute the frequency analysis. Only the averaged pulse rate within a preselected time section requiring a storage unit having a large storage capacity, and requiring a lengthy calculation time since the calculation amount is large is detected. Only noise produced in the regular mode which cannot acquire a change in the respective pulse waves and fluctuations of pulsations and the like is recognized as noise. However, noise which is produced in the irregular mode cannot be discriminated from the pulse wave signal. Under such a circumstance, higher discriminative improvements are required in the conventional pulse wave detecting apparatus.
The present invention has been made to solve the above-described problems of the conventional pulse wave detecting apparatus, and therefore, has an object to provide such a pulse wave detecting apparatus clearly capable of discriminating pulsation from noise, while requiring a small storage capacity of acquired data and also a small calculation amount in a calculation of a pulse wave detection.
To achieve the above-explained object, a pulse wave detecting apparatus (first arrangement) is provided, according to an aspect of the present invention, featured by comprising: pulse wave detecting means for detecting a pulse wave; pulsation predicting means for predicting timing of a pulsation based upon the pulse wave detected by the pulse wave detecting means; range determining means for determining predetermining widths located before/after the timing of the pulsation predicted by the pulsation predicting means; pulsation subject extracting means for extracting a subject for pulsation from the pulse wave detected by the pulse wave detecting means in the predetermined widths determined by the range determining means; and pulsation specifying means for specifying a pulse among the subjects extracted by the pulsation subject extracting means.
In the pulse wave detecting apparatus of the present invention, since the pulsation is detected from the pulse waves located in the predetermined widths before/after the predicted timing of the pulsation, the data used to detect the pulsation can be reduced. Also, while such a storage unit having a large storage capacity used to detect the pulsation is not required, a calculation amount required to detect the pulsation is also reduced.
Also, in the pulse wave detecting apparatus having the first arrangement, such a pulse wave detecting apparatus having a second arrangement according to the present invention is provided in which the pulsation predicting means predicts the timing of the next pulsation movement based upon an interval of a previously acquired pulsation, or a pulse rate.
In the pulse wave detecting apparatus having either the first arrangement or the second arrangement, such a pulse wave detecting apparatus having a third arrangement according to the present invention is provided in which the pulsation specifying means determines a pulse based upon both the timing predicted by the pulsation predicting means and the timing of the pulsation subject extracted by the pulsation subject extracting means.
Further, in the pulse wave detecting apparatus having the third arrangement, a pulse wave detecting apparatus having a fourth arrangement according to the present invention is provided in which the range determining means subdivides the predetermined widths located before/after the predicted timing of the pulsation into a plurality of zones containing both a first zone located earlier than the predicted timing of the pulsation and a second zone subsequent to the first zone which contains the predicted timing of the pulsation, and determines the predetermined widths; and the pulsation specifying means immediately specifies a pulsation subject which is first detected in the second zone as the pulsation.
Further, a pulse wave detecting apparatus is provided, a pulse wave detector to detect a pulse wave; a pulsation predicting circuit to predict timing of a pulsation based upon the pulse wave detected by the pulse wave detector; a range determining circuit to determine predetermining widths located before/after the timing of the pulsation predicted by the pulsation predicting circuit; a pulsation subject extracting circuit to extract a subject for pulsation from the pulse wave detected by the pulse wave detector in said predetermined widths determined by the range determining circuit; and a pulsation specifying circuit to specify a pulse from among the subjects extracted by the pulsation subject extracting circuit.